proj-imim:
Re: PTPicker and 8mm Sigma
Peter Murphy 2000-May-25 00:52:46
Terence Hogben wrote:
> Hello all.
> I have shot some difficult Panos recently and i have been
> procrastinating before starting them because of all the
> difficulties that i am now facing.Bar shots with detailed roof
> and floor 800 iso film evening.
> Nearly left this little detail out, 3 shots.
> The scanning on the Nikon LS 2000 introduces all kinds of
> errors the neg is not centralised in the holder, and sometimes
> i think there is a guasian blur hidden in the scanner.
> Anyway when using PTPicker and carefully chosing my points
> when i choose optimise it only seems to optimise for a split
> second hardly enough time to see the dialog, is this normal?
> Now the result seems allright but parts of the image lean ie
> the left hand side leans out left and the right to the right.
> How is this leaning solved, is vertical determined by the first
> image, and is making sure that it vertical a solution ?
> Or should i manually stitch when shooting in very tight error
> prone areas.
> Would it be better with detailed zenith areas to shoot the above
> shot and insert it at a later point by extracting and reinserting after
> stitching such as Peter Murphys tutorial, or is anybody getting great
> results starting off with PTPicker.
>
Terence
I wrote some notes on "Fixing unlevel panos" for the qtvr list
http://www.iqtvra.org/ml/199909/0095.html
Helmuts reply is here:
http://www.iqtvra.org/ml/199909/0096.html
-the archives are searchable with an engine here:
http://www.iqtvra.org/home.php3?id=5
PSphere to Psphere conversion works on the Mac so you should
be able to use the visual shortcut I describe - ie constrain the
pano so you cant look up and down and set it to max vfov -
then pan around slowly til you see where the tilt is greatest up
or down - at this point scene verticals will be vertical in the
viewer. Then adjust the yaw so that this scene feature is in
the centre of the pano image (use yaw values with the adjust tool
or recentre the pano manually with Photoshop)
This image centre point has zero roll and maximum pitch so you can now
finetune your pitch adjustment with PSphere to PSphere with the
Adjust tool without worrying about trying two sets of values
(ie pitch and roll) - ie just use pitch.
But usually now I dont bother with this and just try
various pitch and roll values til it looks better. Use small proxies and
you can try plenty of combinations quickly.
With a PC you might have to use the intermediate cubic conversion
step I describe to correct a PSphere for roll and pitch.
Alternatively as you say you can try setting nonzero roll and pitch
values for Image 0. This you can do first with the Perspective tool
by eye with the first image if there are horizon cues, or vertical or
horizontal features in the image. ie for example, if the horizon is
visible try different pitch values with the Perspective tool til
the horizon feature is dead centre in the frame (vertically) Use
the Photoshop Info window. You can use small proxies here too.
This use of the horizon for setting the first image values or for
getting subsequent images into the "ballpark" is very handy
for wildly tilted/rolled rapid handheld sequences. Also essential for
handheld multirow rooftop sequences eg - here the horizon
is very often visible in most shots.
As Helmuts reply says there are some features with the Optimizer
for telling it that
certain control points have the same vertical or horizontal values
but I havent got my mind round how they work. This would be
a more elegant solution.
Re Nikon scanner - this is a pain the way it is impossible to
scan repeatably relative to the negative. With circular images
you can select the first image circle, copy and paste into a new
image, go back to the first, convert the selection to a path,
save it. Open the next image, drag the path from the first image
into the second, use the pointer tool to move the image so it
coincides with the path, convert to a selection, copy paste ...
get the next image etc etc
Helmut has a feature which will crop to the circle but I find it
better to do it manually. With digital circles you dont need to
do any of this but if the circle is not central in the frame
you will need to optimize d and e values to get perfect
control point matches
Re getting zenith and nadir detail. If they are important
you will have to either shoot a horizontally rotating sequence
of shots, tilt the lens deliberately
or do extra shots up or down, or do multiple rows,
or use a greater than 180 coverage lens. With extra up and
down shots I havent had much luck with the Optimizer getting
them to stitch automatically so usually I go the extract a view,
fill the hole route.
I wrote some notes on the mechanics of up and down shots
for the qtvr list too -
http://www.iqtvra.org/ml/199907/0058.html
cheers
Peter Murphy
www.culture.com.au/virtual